JP3305758B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having a wide annular groove at a substantially central portion of a tread portion of a tread, and particularly to a pneumatic radial tire having excellent drainage performance even when the tread is completely worn. This guarantees the performance of

[0002]

2. Description of the Related Art A conventional pneumatic radial tire of this type is disclosed in Japanese Patent Laid-Open Publication No. Sho 61-60304. It has a circumferential main groove having a large depth. In such pneumatic radial tires,
Under the action of the circumferential main groove, the wet performance of the tire can be enhanced.

[0003]

However, in the prior art, the circumferential main groove is formed only by changing the thickness of the tread rubber, and the radial carcass and the belt are formed in the crown portion of the tire. Are arranged with a tendency to project outward in the radial direction as a whole in the cross section in the tread width direction, similarly to a conventional general radial tire. The depth of the groove cannot be made sufficient, and therefore,
When the tread is completely worn, that is, when the depth of at least part of the circumferential or width direction groove is 1.6 mm or less, the negative rate becomes almost or completely zero and the tire becomes wet. There is a problem that performance cannot be exhibited.

[0004] Therefore, even when the tread is completely worn, the vulcanization molding of the tire is performed simultaneously with the formation of the circumferential main groove by the vulcanization mold, in order to secure a required negative rate even when the tread is completely worn. It has been proposed to form radially inwardly grooved grooves in each of the arranged radial carcass and belt, and according to this, each of the radial carcass and the belt is constricted by the groove. Since the constricted portion forms a circumferential main groove in cooperation with the tread, the depth of the circumferential main groove can be increased as required, so that the tread is completely It is stated that, even if worn, the action of the constriction can ensure a sufficient negative rate to provide the required wet performance.

However, in the tire molded in the vulcanization mold in this manner, the portion of the belt corresponding to the constricted portion has a small amount of diameter expansion during vulcanization molding, while Since the diameter of each side portion located across the constricted portion increases, the belt portion corresponding to the constricted portion particularly increases in diameter when filling the completed tire with the internal pressure. The occurrence of the protrusion phenomenon at the groove bottom portion of the groove, in other words, a decrease in the circumferential main groove depth is inevitable.

In order to reduce the depth of the circumferential main groove,
It is conceivable to cope by pressing down only the outer peripheral side portion of the groove formed in the belt with a diameter-enhancing constraint layer formed of a cord extending substantially in the circumferential direction of the tread. In addition to making the circumferential main groove depth shallower by a depth corresponding to the thickness of the diameter expansion constraining layer and the like, under the condition of use of the tire, the extending direction of the belt layer cord is There is an inconvenience that the part pressed down by the above and the other part greatly differ.

SUMMARY OF THE INVENTION The present invention has been made as a result of studying to solve the above-mentioned problems of the prior art, and an object of the present invention is to meet a required condition even when a tread is completely worn. Provided is a pneumatic radial tire that can sufficiently prevent the annular groove from protruding at the time of filling the internal pressure into the tire without providing a special diameter expansion restriction layer, as well as being able to secure a negative rate. To be.

[0008]

SUMMARY OF THE INVENTION A pneumatic radial tire according to the present invention has a belt and a tread which are recessed radially inward at substantially a central portion of a tread tread portion, that is, at a central portion or a portion in the vicinity thereof. At least an annular groove having a large depth and a large width is provided, and between the belt and the tread, an organic fiber cord extending substantially in the circumferential direction of the tread, and having at least a width substantially equal to the belt width. While providing one cap reinforcing layer, the organic fiber cord density of the cap reinforcing layer only in a portion corresponding to the annular groove was set to a range of 1.15 to 2.0 times that of the other portions. Things.

Here, "a portion corresponding to the annular groove" means a portion corresponding to the entire width of the annular groove,
Alternatively, a portion corresponding to a somewhat narrower range is meant, and at least a portion corresponding to the groove bottom of the annular groove is always included in the portion.

[0010]

[Function] In this pneumatic radial tire, the radial carcass, of course,
By providing an annular groove in which both the belt and the tread are depressed inward in the radial direction, the depth of the annular groove can be reduced even if the tread is completely worn. As a depth sufficient to secure the rate, it is possible to ensure the excellent wet performance at all times.

In this tire, a cap reinforcing layer, which is mainly applied to a high-performance tire and protects the tread against centrifugal force and has substantially the same width as the belt, is used. In the part corresponding to the groove, the cord density of the organic fiber cord forming the cap reinforcing layer is made larger than that of the other parts, so that the vulcanization molding of the green tire and the filling of the finished tire with the internal pressure can be performed at the same time. Under the action of the cap reinforcing layer is constrained over the entire width thereof, and in particular, the portion of the cap reinforcing layer where the cord density is high, corresponding to the annular groove, is particularly greatly constrained. Will be.

Therefore, when filling the tire with the internal pressure, the protrusion of the annular groove due to the expansion of the belt can be effectively prevented, and the decrease in the depth of the annular groove can be sufficiently prevented. In addition, here, since the protrusion of the annular groove can be prevented by the cap reinforcing layer itself, the depth of the annular groove itself should be made deeper than in the case of the related art in which a special diameter expansion restriction layer is provided. Can be.

By the way, the cap reinforcing layer here restricts the expansion of the belt not only at the portion corresponding to the annular groove but also over almost the entire width of the belt. The difference between the extending direction of the belt layer cord of the corresponding belt portion and the cord extending direction of the other belt portion is significantly reduced as compared with the case where the diameter expansion of only the belt portion corresponding to the groove is restricted. Can be.

Here, the cord density of the cap reinforcing layer is not only increased rapidly at the portion corresponding to the annular groove, but also gradually increased to the portion corresponding to the groove bottom of the annular groove. According to the latter, in particular, according to the latter, the extending direction of the belt layer cord between the portion corresponding to the annular groove and the portion not corresponding thereto and in the portion corresponding to the annular groove is gradually changed so that the annular groove is formed. Thus, it is possible to form an optimal constraining layer according to the shape, and to uniformly and effectively prevent the protrusion of the annular groove.

In the tire, the cord density of the portion of the cap reinforcing layer corresponding to the annular groove is set to 1.15 to 2.0 times that of the other portion, so that the cord extending direction of the belt portion corresponding to the groove is increased. Can be effectively prevented without making the annular groove protrude so much in the extending direction of the belt layer cord of the other part.

That is, if it is less than 1.15 times, the amount of protrusion of the annular groove cannot be reduced as expected, so that when filling the tire with the internal pressure, the depth of the annular groove due to the diameter expansion of the belt is reduced. The reduction occurs and the negative rate when the tread is completely worn cannot be maintained at the expected value.

On the other hand, if it exceeds 2.0, the cord extending direction of the belt portion corresponding to the annular groove is largely different from the cord extending direction of the other belt portions as in the case of the prior art. In addition, the change in the force for restraining the belt is large at the belt portion corresponding to the annular groove, and the distortion of the belt at the end of the portion becomes extremely large, so that a problem easily occurs in belt durability.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view in the tread width direction showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a radial carcass composed of one carcass ply. Here, each side end portion of the radial carcass 1 is wound up from the inside to the outside around the bead core 2 and fixed. On the outer peripheral side of the radial carcass 1, a belt 5 formed of at least two belt layers 3 and 4 made of respective steel cords extending crossing each other is disposed, and further on the outer peripheral side of the belt 5 Is provided with a tread 6.

At the center of the tread tread portion 7 in the width direction, an annular groove having a sufficiently large width and depth formed by indenting both the radial carcass 1 and the belt 5 and the tread 6 inward in the radial direction is provided. 8, and a cap reinforcement layer 9 formed by spirally winding an organic fiber cord, for example, to the full width of the belt, is disposed between the belt 5 and the tread 6.

Here, the cap reinforcing layer 9 is
As can be seen from the exploded perspective view of FIG.
In the corresponding part 9a, the code density of the other parts is 1.15
~ 2.0 times.

According to the tire configured as described above,
The annular groove 8, under its sufficient width and depth, can ensure the expected negative rate even when the tread 6 is completely worn. Further, since the cap reinforcing layer 9 restricts the diameter expansion of the belt 5 over its entire width, even if the diameter expansion of the belt portion corresponding to the annular groove 8 is particularly greatly restricted, as described above, The difference between the cord extending direction of the belt portion and the cord extending direction of the other belt portions can be sufficiently reduced.

Here, as shown in FIG. 3, the code density of the cap reinforcing layer 9 at the portion 9a corresponding to the annular groove 8 is 1.15 times or more that of the other portions. The amount of protrusion of the annular groove 8 can be made sufficiently small. On the other hand, when the cord density exceeds 2.0 times that of the other portions, as described above, the cord extending direction of the belt portion corresponding to the annular groove 8 is changed with respect to the cord extending direction of the other portion. , As in the prior art.

By the way, as shown in FIG. 4 (a), the cord density of the cap reinforcing layer 9 is increased more rapidly at the portion 9a corresponding to the annular groove 8 than at the other portions, and In addition to keeping the code density constant in the portion 9a, as shown in FIG. 4 (b), the code density is gradually increased in the portion 9a toward the groove bottom corresponding portion, and the code density is increased in the groove bottom corresponding portion. The density may be constant, and in any case, the cap reinforcing layer 9 may be formed by spirally winding one or a plurality of organic fiber cords over the entire width thereof, or reducing the cord density. The belt 5 can be formed by independently spirally winding each of the small portion and the large portion. In addition, a belt-like body in which a plurality of organic fiber cords are arranged in parallel with each other is used as the belt 5. Wrap around Kick may be formed by.

When the cap reinforcing layer 9 is provided in two layers, either the inner or outer cap reinforcing layer 9 or both the inner and outer cap layers may have any one of the above-described structures. The required cord density for the entire reinforcing layer can be provided, which also has the desired effect.

[0025]

As is apparent from the above description, according to the present invention, an annular groove having a sufficient width and depth is formed by depressing each of the belt and the tread radially inward. By doing so, it is possible to ensure a required negative rate even in a completely worn state of the tread portion, and to prevent the annular groove from protruding, as in the prior art, for the purpose of preventing the annular groove from protruding. It is not necessary to dispose a special diameter-enhancing constraint layer only at the portion corresponding to the above. Over a wide area.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the tread width direction showing an embodiment of the present invention.

FIG. 2 is a partially developed perspective view illustrating a cap reinforcing layer.

FIG. 3 is a graph showing a relationship between a cord density of a cap reinforcing layer and an amount of protrusion of an annular groove.

FIG. 4 is a diagram illustrating a change state of a cord density of a cap reinforcing layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radial carcass 3, 4 Belt layer 5 Belt 6 Tread 7 Tread tread portion 8 Annular groove 9 Cap reinforcement layer 9a Part corresponding to an annular groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-275005 (JP, A) JP-A-55-8966 (JP, A) JP-A-4-243601 (JP, A) JP-A-61-275601 60304 (JP, A) JP-A-2-147231 (JP, A) JP-A-1-36434 (JP, A) JP-A-2-38102 (JP, A) JP-A-62-290524 (JP, A) JP-B-44-17801 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 9/22, 11/00, 3/00

Claims (1)

(57) [Claims] 1. A pneumatic radial tire comprising: a radial carcass; a belt having at least two belt layers disposed on an outer peripheral side of the radial carcass; and a tread disposed on an outer peripheral side of the belt. Te, substantially in the central portion, provided with an annular groove formed by both recessed radially inward of the belt and tread, between the belt and the tread, substantially organic fiber cords extending in the tread circumferential direction of the tread surface portion And at least one cap reinforcing layer having a width substantially equal to the belt width, and only in a portion of the cap reinforcing layer corresponding to the annular groove , the organic fiber cord density is compared with that of the other portions. And pneumatic radial tires with a range of 1.15 to 2.0 times.